The present invention relates to method and apparatus for controlling an internal combustion engine to prevent the occurrence of knocking.
Various types of anti-knocking control systems to be incorporated with an internal combustion engine have been developed with a view to minimizing the occurrence of knocking concurrently with maximizing the output charactristic of the engine.
Generally, prior art control systems are arranged so as to control ignition timing, air-fuel ratio and the like in accordance with the results of the comparison of the output signal of a knock sensor attached to the engine and a reference established in advance.
To adjust the balance between the maximization of the output characteristic and the knocking prevention, it is the most important that the reference is established adequately in the control, and therefore a number of attempts to meet this requirement have been made hitherto. Such a technique is disclosed in Japanese Laid-Open Patent Application No. 56-115861. However, the prior art systems do not produce satisfactory results for meeting demands imposed in high precise anti-knocking control, because of difficulty of determination of the reference resulting from, for example, mechanical tolerances of engines.